Catalytic cracking



Patented Feb. 1, 1944 CATALYTIC CRACKING Robert F. Ruthrufl, Chicago, 111.

No Drawing. Application July 14, 1941, Serial No. 402,431

16 Claims.

This invention relates principally to the catalytic conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point and to improved contact agents for accelerating said conversion.

The thermal conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point and more particularly into hydrocarbons in the motor fuel boiling range is well known in the art. Such thermal conversion processes suffer from many disadvantages; among these may -be mentioned the comparatively low octane rating of the motor fuel produced and the high production of undesirable products, such as gas and tar, having little commercial value. These and other disadvantages, have led to the development of'various catalytic processes for the conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point and more particularly into hydrocarbons in the motor fuel boiling range.

fuel produced by the catalytic conversion of higher boilinghydrocarbons is of much higher octanerating, the gas production is appreciably less, and the production of material with higher carbon to hydrogen ratio than that of the higher boiling hydrocarbon charge is much decreased.

As contact agents for catalyzing the conversion of higher boiling hydrocarbons into hydrocarbons of lower boiling pointsuch materials as clays and synthetic silica-alumina complexes have been suggested. While these contact agents are fairly satisfactory, they sufier from numerous disadvantages. For example, while the gasoline to gas nearly the same as that of a virgin gas oil. Ac-

cordingly, from a theoretical standpoint, the conversion of this higher boiling hydrocarbon mixture into the lower boiling should proceed almost quantitatively with the simultaneous production of little or no material other than the major product. That this does not occur in either thermal or catalytic conversion processes is well known to thos'. familiar with the art. Further- In. comparison with thermal processes, the motor cially at high temperatures. I the elimination of water vapor from regeneration more, all catalysts known to date for promoting the conversion of higher boiling hydrocarbons to hydrocarbons of lower boiling point decline in activity more or less rapidly with use, due to the deposition of carbon or carbonaceous residues on the surfaces of said catalysts. This necessitates the periodic regeneration of the contact agents employed, this being accomplished-usually by burning the accumulated deposits from the surfaces of said contact agents by use of air or dilute air. The clay contact agents of the prior are suffer a gradual, permanent decline in activity with repeated regeneration. The synthetic silica-alumina contact agents described in the prior art are quite sensitive to water vapor, espe- This necessitates gases prior to passage over the catalyst and seriously limits the amount of steam that may be used in the catalytic conversion step to aid in vaporizing the hydrocarbon charge. My improved catalysts for theconversion of hydrocarbons of higher boiling point to hydrocarbons of lower boiling point do not exhibit the disadvantages shown by contact agents described in the prior art or exhibit these disadvantages to a less marked degree.

One object of my invention is to provide an improved process for the catalytic conversion of hydrocarbons of higher boiling point to hydrocarbons of lower boiling point and improved contact agents for accelerating said conversion.

A further object of my invention is to provide an improved process for the catalytic conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point which results in a high yield of desirable conversion products and a low yield of undesirable conversion' products and improved contact agents for accelerating said conversion.

An additional object of my invention is to provide an improved process for the catalytic conversion which exhibit increased resistance to deterioration in the presence of steam in comparison with hitherto known contact agents.

Other objects of my invention will become evident as the description thereof proceeds.

My improved catalysts for the conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point are-synthetic magnesium silicates containing more or less water of hydration. The desired materials are made by hydroxide) sired physical form prior to use as a contact agent.

Many natural and synthetic magnesium com- 1 pounds exhibiting the large specific surface, relatively low solubility and other attributes requisite for the purposes of this invention are known. Among these maybe mentioned natural magnesite (magnesium carbonate), synthetic magnesium carbonate, natural brucite (magnesium synthetic magnesium hydroxide, magnesia, and basic magnesium carbonates. Especially suitable is a basic magnesium carbonate synthetically produced in the same manner as that commonly followed in manufacturing this product for heat insulation purposes. To facilitate reaction with the material of siliceous nature selected, it is desirable that the relatively insoluble magnesium compound employed exhibit a large specific surface. with natural minerals this can be attained by grinding them to an extreme state of subdivision, for example, so that the ground material is finer than 100 mesh, preferably finer than 200 mesh. Synthetic magnesium compounds suitable for the purposes of this invention are usually obtained as precipitates having a large specific surface. This is especially true if the precipitates are not dried prior to hydrothermal reaction with the siliceous material selected and even more particularly if the precipitates are subjected to hydrothermal reaction with the siliceous material as soon as possible after their preparation by precipitation. Even if precipitated magnesium compounds are dried prior to use they exhibit a relatively high specific surface and may be easily reduced to a fine state of subdivision by a light crushing or grinding operation. Usually a natural magnesium mineral cannot be reduced mechanically to a product exhibiting as high a specific surface as a precipitated magnesium compound. This fact must be borne in mind when determining the conditions to be employed in the hydrothermal reaction with the siliceous material selected.

Generally speaking, the above mentioned considerations also govern the selection of the silithis invention. Among these may be mentioned silica gel, especially in finely ground or finely divided form. Methods for the production of silica gel in finely divided form are described in my copending application, Serial Number 401,329, filed July '7, 1941. Even better adapted to the purposes of this invention is washed silica hydrogel.

The speed of the hydrothermal interaction between the selected magnesium compound and the selected siliceous material may be greatly accelerated by employing certain promoters such as alkali metal carbonates, hydroxides and silicates. Obviously, when such promoters are employed, the desired magnesium silicate catalyst is formed in alkaline medium. It has been found that even small amounts of alkali metal compounds in the finished catalyst seriously affect the activity thereof. Furthermore, it has been observed that when formed in alkaline medium it is diilicult to remove alkali metal compounds from the resulting magnesium silicates by water washing.

However, it has been found possible to removealkali metal compounds easily and completely from magnesium silicates prepared in alkaline medium by washing the precipitates with dilute acid and then with water. A solution of an ammonium compound, for example, ammonium chloride, may be used instead of dilute acid to accomplish the same end.

It is obvious that alkali metal silicates serve a dual role in the reaction. acting as promoters as well as serving as a source of siliceous material. If desired, alkali metal silicates can be used in the absence of any other natural or artificial siliceous material in the preparation or the catalysts of this invention.

' Even when a promoter of the types above mentioned is not employed in the manufacture of the magnesium silicate catalysts of this invention. frequently "the precipitation occurs in slightly alkaline medium. While contamination by added alkali metal compounds is not involved, it has been observed that here also the activity or the magnesium silicates may be increased by washing them with dilute acid and then with water.

It is evident that the catalysts of this invention are a magnesium silicate pseudomorph of a magceous material which is to undergo hydrothermal reaction with a suitable magnesium compound.

- The siliceous material should be in a form exin this invention. For example, the plate like silica obtained upon drastically acid treating vermiculite, for example. as described in U. 8. Patent 1,898,774, issued February 21, 1933, to Robert G. Guthrie and Oscar J. Wilbor, is very reactive, especially after the. product has been wet ground to separate the decks of laminae yet further and reduce the individual plates to even smaller size.

Also, by drastically acid treating a'clay, especially a clay of the montmorillonitic or bentonitic type, a siliceous residue is obtained that is suitable for the purposes of this invention. Certain artificial siliceous materials are even more suitable than natural products for the purposes of nesium carbonate. In the preparation of these a magnesium carbonate, having a characteristic lattice structure and crystal form is converted into a magnesium silicate still possessing the characteristic lattice structure and crystal form of the original magnesium carbonate. In other words. the C0: group is replaced by the SiO: group but the resulting silicate exists in the characteristic lattice arrangement and crystal form of the original carbonate.

For the better understanding of this invention, examples describing the preparation of magne sium silicate catalysts suitable for the purposes thereof are included. It is to be understood that these examples are illustrative only and the spirit and the scope of the present invention are in no way to be limited thereby.

Example 1 A high grade magnesite (natural magnesium carbonate) is calcined and the resulting magnesia is wet ground to form a slurry which is then treated with carbon dioxide (obtained, if desired, from the calcining step) to form magnesium carbonate and magnesium bicarbonate. On boilin a basic magnesium carbonate is precipitated and is separated by filtration, is washed but not dried.

Five hundred volumes of sodium silicate solution containing 8.85% NazO and 28.5% S10: are diluted with a like amount of water. The thus 7 diluted solution and 625 volumes of 6N sulfuric is not dried.

An amount of the wet, washed, basic mag- -nesium carbonate precipitate equivalent to 40 pounds of magnesia and an amount of the wet,

washed, silica-hydrogel equivalent to 60 pounds silica are added t 150 gallons of water, the water present in the wet precipitates being included in this figure. Twenty-five pounds of sodium car; bonate are added and the slurry is agitated and brought to a boil, beingmaintained at this tem-' 'peratureTdr five hours.

The solid is then removed by filtration and is washed once or twice with water, preferably by being made into a slurry with water and then filtered. The thus partially washed material is made into a slurry with dilute sulfuric acid and is then filtered, this operation being repeated twice. Finally, the product is washed 4 to 6 times with water by being made into a slurry with water and then filtered.

Example 2 Similar to Example 1 except that the silica equivalent of the wet, washed silica hydrogel' taken is cut to 13 pounds and the sodium carbonate is replaced with 165 pounds sodium silicate solution N brand, Philadelphia Quartz C0,), the water added to bring the total to 150 gallons being corrected for the water added with the water glass.

Example 3 Similar to Example 1 except that no wet, washed, silica hydrogel is employed, this material being replaced by 210 pounds of sodium silicate solution (N brand, Philadelphia Quartz Co.) The 150 gallons water used in this preparation inc1 ude the water added with the washed, wet, basic -magnesium carbonate and with the sodium silicate solution.

' Example 4 Similar to Example 1, except no sodium carbonate was added. The hydrothermal reaction was conducted in an agitated'autoclave at 500 pounds pressure and the temperature corresponding thereto for a period of 4 hours, carbon dioxide being periodically discharged from the autoclave.

If desired, the magnesium silicate contact agents of the instant invention may be activated or treated with activators prior to use. lysts may b improved to a greater or less degree by giving them a light treatment at elevated tempelatures with a dilute acid such as sulfuric acid or hydrochloric acid. Or, a small amount, for example, 5% by weight, of hydrofluoric acid may be added to the catalyst and the resulting mixture gently calcined. After these acid treatments the catalyst is preferably water washed thoroughly before use. These treatments seem to gated conduit at elevated temperature.

The catanesia and silica respectively. 'If desired, both treatments may be applied to a single catalyst.

Certain beneficial results follow the addition of selected activators in relatively small amounts to the catalysts of the instant invention. These activators may be added during the preparation of the catalysts of the instant invention or-the finished catalysts may be impregnated with thermally decomposable salts of the activators following which the impregnated catalysts are calcined. Among activators found to be more or less beneficial may be mentioned boric oxide, beryllia, thoria, zirconia and alumina. About 5% or less of these activators, based on the weight of the catalyst, may be used.

The washed magnesium silicates prepared in accordance with the above examples or otherwise are further processed for the production of the final catalyst, the exact procedure followed depending on the conversion process to be employed. Processes for the conversion of higher boiling hydrocarbons into hydrocarbons of lower boing point may conveniently be classified into three broad groups, as follows:

a. Fixed bed conversion processes-In these the higher boiling hydrocarbon charge, preferably in the vapor state, is passed through a vessel containing the contact agent. Periodically, the hydrocarbon charge is diverted to a second vessel containing contact agent, while the contact agent in the first vessel is regenerated by the removal of carbonaceous deposits from the surface thereof by burning with air or dilute air, following which the charge is again passed therethrough,

11. Moving bed conversion processes-In these the higher boiling hydrocarbon charge, preferably in the vapor state, is passed through a vessel through which the contact agent is moving either continuously or intermittently. The contact agent discharged passes to another vessel in which regeneration occurs. this being accomplished by moving the contact agent through said vessel and contacting it at elevated temperature with air or dilute air. The contact material dischargedfrom the regeneration vessel is then conveyed to the inlet of the reaction vessel.

0. Conversion processes with powdered contact agent.-In these, the higher boiling hydrocarbon charge, preferably in the vapor state, is passed through an elongated conduit, the powdered contact agent being suspended in the charge and moving with it. On leaving this first conduit, the hydrocarbons are separated from the contact agent, while the contact agent is suspended in air or dilute air and is passed through a second elon- Contact agent is separated from the suspended fluid after discharge from this second conduit, the thus regenerated and separated contact material then being mixed'with high boiling hydrocarbon charge for repassage through the first elongated conduit.

It is evident that a highly pulverized contact agent is desirable for processes 0. while contact material in the formof aggregates of reasonable size and strength is desirable for'processes a and b. By simply drying the washed magnesium silicates made according to the above examples or otherwise, a cake is obtained which is quite friable and easily pulverized to give a finely divided material eminently suited for processes'c. For making the contact material into aggregates of appreciable size and strength, suitable for use in processes a and b. several procedures may be employed, some of them being described briefly below:

I. The contact agent, after drying, is pelleted in a pill machine, a binder being used if necessary.

II. The magnesium silicate contact agent is dried to a moisture content of 25-40% and then is passed through an extrusion machine. The resulting spaghetti is cut to form cylinders of the desired size either before or after final drying. If desired, the damp magnesium silicate may, prior to extrusion, be mixed with a suitable binding agent, clay for example.

III. A portion of the washed precipitate of magnesium silicate is dried and is then mixed with the remaining undried filter cake to give a mixture having a moisture content proper for extrusion. If desired, during the mixing of the undried and dried cakes a suitable binder may be added. Then proceed to extrude the mixture as in II.

In the application of these contact agents prepared as above described or otherwise to the conversion of higher boiling hydrocarbons to hydrocarbons of lower boiling point, the higher boiling hydrocarbon charge, preferably in the vapor state, may be contacted with the catalysts of this invention at atmospheric or elevated pressure and at temperatures of from 800 to 1050 F., more or less, preferably in the temperature range 875 to 1025 F., more or less. When operating in accordance with process a above, from 1 to 4 liquid volumes of feed, more or less, may be charged per hour per volume of catalytic reaction space.

Example 5 1.1% by weight gas and 0.6% by weight of coke.

At equal gasoline conversion, a typical silicaalumina catalyst gave 250% as much gas and 150% as much coke.

Example 6 Since the magnesium silicates of the instant invention are only moderately active, the experiment of Example 5 was repeated at 1000 F., the charge rate being increased to 2.25 liquid volumes per hour volume of catalytic reaction space. The gasoline yield was 25% The capacity of the unit (volumes of gasoline produced in unit time) was increased 2.5 times in comparison with Example 5. The excellent product distribution of Example 5 was again observed.

Because of the favorable activity of the catalysts of this invention at relatively elevated catalytic cracking temperatures, the favorable product distribution resulting from the use of these contact agents even at relatively elevated catalytic cracking temperatures and since these materials are insensitive to steam they are especially suitable for use as contact agents for the conversion of such materials as reduced crudes. heavy gas oils, heavy viscosity breaker gas oils '(both thermal and catalytic), heavy coker gas oils and the like to hydrocarbons of lower boiling point, particularly gasoline. Since the catalytic conversion reaction is preferably conducted in the vapor phase, when stocks of high boiling point. such as those mentioned above, are processed, a high operating temperature is preferably used in order to achieve vapor phase conditions. when contact agents of the prior art are employed at such high operating temperatures, theratio of the desired conversion product toundesired conversion products is low which is notthe case when the catalysts of the instant invention are used. Additionally, steam does not injure the contact agents of the instant invention and accordingly steam may be used to aid in the vaporization of the charging stocks, this being particularly helpful when unusually" high boiling materials such as those enumerated above are employed. Steam adversely affects the activity of contact agents of the prior art to a greater or less degree.

While this invention has been described through the medium of specific details and specific examples thereof, it is to be understood that the invention is not in any way to be limited thereby except insofar as such limitations appear in the appended claims.

I claim: i

1.A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time sufilcient to effect substantial conversion, with the product of the hydrothermal interaction of a finely divided siliceousmaterial and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

2. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time sufficient to effect substantial conversion, with the product of the promoted hydrothermal interaction of a finely divided siliceous material and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

3. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors,

at a cracking temperature for a time sufiicient to effect substantial conversion, with the product of the hydrothermal interaction of finely divided quartz and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

4. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling. point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time sufllcient to eflect substantial conversion, with the product of the promoted hydrothermal interaction of finely divided quartz and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

5. A method of converting hydrocarbons of boil ng hydrocarbons and contacting the vapors, at a cracking temperature for a time suilicient to effect substantial conversion, with the product of the hydrothermal interaction of finely divided diatomaceous earth and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

, bonate.

6. A method of converting hydrocarbons oi. higher boiling point into hydrocarbons or lower boiling point comprising vaporizing saidhigher boiling hydrocarbons and contacting the vapors,

at a cracking temperature for a time sufiicient to effect substantial conversion, with the product of the promoted hydrothermal interaction of finely divided diatomaceous earth and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

7. A method of converting hydrocarbons of 11. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling'pointcomprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time sumcient to effect substantial conversion, with the product of the hydrothermal interaction of finely divided diatomaceous earth and finely divided basic maghigher boiling point into hydrocarbons oilower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time suificient to eflect substantial conversiori, with the product of the hydrothermal interaction 01' finely divided silica hydrogel and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium carbonate.

8. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature tor a time sufiicient to efiect substantial conversion, with the product of the promoted hydrothermal interaction 01- finely divided silica hydrogel and a finely divided substance selected from the group consisting of basic magnesium carbonate and magnesium car- 9. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time sufficient to effect substantial conversion, with the product of the hydrothermal interaction of finely divided the promoted hydrothermal interaction of finely divided quartz and finely divided basic magnesium carbonate. I

nesium carbonate.

12. A method of converting hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors, at a cracking temperature for a time sufiicient to efiect substantial conversion, with the product 0! the promoted hydrothermal interaction of finely divided diatomaceous earth and finely divided basic magnesium carbonate.

13. A method of converting hydrocarbons oi higher boiling point into hydrocarbons of lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting the vapors. at a cracking temperature for a time sufiicient to eiifect substantial conversion, with the product oi.-

the hydrothermal interaction or finely divided silica hydrogel and finely divided basic magnesium carbonate.

p 14. A methodot converting hydrocarbons of higher boiling point into hydrocarbons oi lower boiling point comprising vaporizing said higher boiling hydrocarbons and contacting'the vapors,

at a cracking temperature tor a time sufiicient to effect substantial conversion, with the product of the promoted hydrothermal ,interactitm of-finely divided silica hydrogel and finely divided basic magnesium carbonate.

15. A contact agent for catalyzing the conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising amagnesium silicate pseudomorph 0! a magnmium carbonate.

. '16'. A contact agent for catalyzing the conversion of hydrocarbons of higher boiling point into hydrocarbons of lower boiling point comprising a magnesium silicate pseudomorph of basic magnesium carbonate.v 

